663557681 has 4 divisors (see below), whose sum is σ = 663625200. Its totient is φ = 663490164.

The previous prime is 663557677. The next prime is 663557683. The reversal of 663557681 is 186755366.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is not a de Polignac number, because 663557681 - 2² = 663557677 is a prime.

It is a super-2 number, since 2×663557681² = 880617592028195522, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (663557683) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 15851 + ... + 39728.

It is an arithmetic number, because the mean of its divisors is an integer number (165906300).

Almost surely, 2^663557681 is an apocalyptic number.

It is an amenable number.

663557681 is a deficient number, since it is larger than the sum of its proper divisors (67519).

663557681 is a wasteful number, since it uses less digits than its factorization.

663557681 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 67518.

The product of its digits is 907200, while the sum is 47.

The square root of 663557681 is about 25759.6133705458. The cubic root of 663557681 is about 872.2203737166.

The spelling of 663557681 in words is "six hundred sixty-three million, five hundred fifty-seven thousand, six hundred eighty-one".